Why is Axeman Andersen considered the Best?

Hi All,

Welcome to WINTER!

I want to put in a boiler soon. Initially I'll be using it with a heat exchanger coil in my forced air furnace and a couple of fintube zones plus domestic water. The boiler will be installed in my cellar. I need a about 120,000 btu's output to heat my 165 year old farmhouse. (That will be lessened dramatically as I'm renovating!)

Why are the old Axeman Andersen stoker boilers so highly prized and so many say they are the best coal fired boiler made?

What other stoker/hopper fed boilers are generally considered premo?

Personally what does it for me is the fact that units from 1948,1950,1958, 1954 and still working today with minor wear. you can still buy these units new altho 6300 for AA130M which is 130,000 BTUs or there is the AHS 130s which is 130,000 BTUs. The AHS is a take off of the AA's but has minor changes done to them, some maybe good some maybe not that is up in the air for me.

As U235 said they're a quality built indestructible unit. In addition they are the most efficient design out there, the AHS shares many of the Axeman design attributes and is also very efficient.

The Keystoker, EFM and Harman companies are three manufactures that support existing and past designs of their boiler models. IMO any boilers made by these companies would make a decent selection. If you are looking for a used unit you should check with the manufacturer and make sure parts are still available. None of these three are as efficient as the Axeman/AHS design but each has their strengths and if the price is right are an equally desirable choice.

Best of luck with your search.

The Eshland, now AHS boilers are in my opinion an improvement on the A-A design. The AHS uses two independent motors. One for the combustion blower and one for the ash grate control. Since they are independent you have more choices on how you choose to control them. The A-A uses a flat plate type domestic coil. The AHS a 4 inch pipe thread type. The pipe thread type is a widely used off the shelf product that is less expensive because it has more usage than the flat plate seal type. These are usually custom for a particular boiler. The thread type is also arguably less prone to leaks because it's easier to seal a thread. The AHS has greasable grate rollers, the A-A does not. It's an improvement but there's likely no real need for it.

The big difference in current standard products is the method of feeding coal to the boiler. The A-A has a helicoid flighting type auger. It makes noise and coal fines. The standard AHS is manual feed hopper atop the boiler. AHS options include the helicoid flighting or screw auger.

The A-A uses a old style radiant heat sensor to control the grate. The AHS temperature grate control option uses a thermocouple with a PID controller. A more precise type sensor.

Both the A-A and AHS boilers beg for modern electronic controls. There is nothing available the integrates all the needed functions. Hint: Coaltrol designers, there may be a new product development here. I have a AHS S130. Knowing what I know today I would buy it again, but with a Honeywell AQ475A Aquatrol Outdoor Temperature Compensator in place of the standard aquastat. I would buy the belt drive option without a motor. I would install my own totally enclosed fan cooled variable speed 1/2 HP drive motor. I'd select a motor controller that allowed me to ramp up the blower speed. This would first expel the built up gases that likely cause the "bumps". It could also run at a lower speed during off times, making a direct vent boiler. It would also allow me to select the optimum combustion air for maximum combustion efficiency. I would use a type J thermocouple controller for measuring ash temperature. Where I would sense the temperature is unknown. It's not clear to me that poking the thermocouple in the ash is the right place.

All of this would not be cheap but would have enough adjustment possibilities for different coal quality and draft conditions. It would also permit year round heating of domestic hot water with reasonable standby losses.

Yanche wrote: The A-A has a helicoid flighting type auger. It makes noise and coal fines.

I'll add the A-A's are prone to "clog up" for lack of better term. This can result if your coal already has a lot of fines in it from delivery. It shouldn't but sometimes this can be unavoidable particularly if its the middle of winter. As far as the noise goes its really minimal and you become used to it.

EFM makes an excellent underfeed boiler and the parts are readily available. Keystoker makes a real nice flat grate boiler as well. If you can see one operate you'll appreciate the differences. A/A and AHS seem to be much more complicated but just as good.

Thanks guys, I really apreciate your advice and knowledge!
It's truly a challenge finding used stoker type stoves, furnaces and boilers. By the time you find one for sale it's already been bought by a Johnnie-on-the-spot with cash in hand!

You just have to be Mr Johnnie-on-the-spot and grab the boiler first!!

Easier said than done !!

Greg L

Hey! I resemble that remark, and my name ain't Johnny.

Matthaus wrote:As U235 said they're a quality built indestructible unit. In addition they are the most efficient design out there, the AHS shares many of the Axeman design attributes and is also very efficient.

The Keystoker, EFM and Harman companies are three manufactures that support existing and past designs of their boiler models. None of these three are as efficient as the Axeman/AHS design...

Efficient, efficient, efficient; is what we all want! To get the most heat, to heat us; not the chimney. Without a picture from a brochure or from a unit that someone owns, it maybe difiicult to answer; but, can anyone tell us exactly what is so unique about the Axeman/ AHS heat exchanger? Does it have an external heat exchanger scraper rod?
Of the three other brands, which is the second runner up; in being efficient. If it is Keystoker, are all of their air stoves and furnaces; of the same efficient design? If it is not Keystoker, has anyone determined which brand has the most efficient air furnace and/ or stove?

Finding efficiency ratings on boiler is impossible. There are no DoE efficiency standards on coal central heating units like there are on oil or gas units. What testing standards there are mostly from the EPA and they apply to stove pollution. Coal equipment manufacturers have no incentive to test their equipment, it's expensive and since there is no test standard the results would close to useless for comparisons. That said you can make some judgments based on design. Most important is combustion efficiency. This is a measure of just that, the combustion process. How much of the BTU content in the coal is converted to heat. The only number I know of is 84% quoted in the Bureau of Mines Report on the A-A 130 boiler. By similarity of design the AHS would have similar numbers. The only two variables you have to adjust on any coal appliance is coal feed and combustion air. In general any appliance in which you can make these adjustment can have good combustion numbers. Equipment to measure combustion efficiency measures flue gas CO, O2 and temperature. Using these numbers on a slide rule calculator gives the combustion efficiency. In effect the slide rule solves the chemistry equation for the fuel you are burning.

BUT that's not the complete story. The efficiency that is also important is transfer of the combustion heat to the boiler water, furnace plentum or stove walls. Here is where the construction makes a big difference. A very simple design would just be a big box with an chimney breach. Very inefficient. Improvements, would have multiple folds of the flue gases with some metal conduction path to transfer this heat to the water or plenum air. Obviously, as the soot or ash builds up on these transfer surfaces the efficiency goes down. Good designs make it easy to clean these surfaces. Here is where the A-A, Eshland and AHS designs shine. All use an internal to the flue path combustion blower. This forces hot combustion air to contact the metal transfer surface and the flinging of the fly ash keeps it clean. In addition the heat in the fly ash gets transfered as it impinges on the metal.

Next is seasonal efficiency. How well the equipment works under different BTU loads. There operational efficiencies also, but I'm tired typing. Maybe later. Bottom line the A-A and AHS boilers are the best. Especially when you also use it to heat domestic hot water and use it year round.

Yanche wrote:Here is where the A-A, Eshland and AHS designs shine. All use an internal to the flue path combustion blower. This forces hot combustion air to contact the metal transfer surface and the flinging of the fly ash keeps it clean. In addition the heat in the fly ash gets transfered as it impinges on the metal.

Bottom line the A-A and AHS boilers are the best.

This sums it up, the A-A gets a slight edge as old man Axeman has a deal with the devil.

I think EFM is the best. Why? because I have one I bought cheap and the EFM guy is on here to answer questions. I rate my boiler as 99.9% efficient. .1% is the dust that blows away when I dump the ashes, that is just waste. The coal completely burns heating the water, it heats the pipes in my basement, it heats the chimney which runs up through 3 floors, the boiler itself radiates heat warming my workshop and the floorboards. Any heat that escapes through the roof de-ices the chimney crown keeping the flue clear of obstruction. About 10% of the coal that is augured in turns to ash, this is fully utilized as ice grip material and driveway fill. A bag of ice melt is $4, driving to the town yard to get buckets of sand for the driveway costs $5 a trip in gas and Pepsi. Bottom line is there isn't any cheaper way than coal to heat a space besides using an axe and chopping firewood from the yard.

Why is Axeman Andersen considered the Best?

I think this is similar to asking why are Chevy's the best. Such questions are best answered late at night while consuming adult beverages.

For me the following factors led me to buy Axeman Anderson:

1. 84% Efficiency: Double-pass fire tube design. It is a central heating boiler plant (no stoves for me, thanks) with domestic hot water coil. The unit has a relatively low stack temperature (A sign of efficiency assuming the proper heat is being delivered to the house).

2. Time tested design-- no known major problems

3. Auger tube/coal bin feed: no bag or hod handling. Infrequent handling (shoveling) of coal using an in-cellar (or boiler room) coal bin. I just didn't want an AHS hopper. My shoulders don't like the overhead lifting. The AHS auger tube adds many $$$ to the price.

4. Fairly-detailed brochure and manual with mechanical drawings and that dandy Bureau of Mines Report with real data to peruse. The AA info badly needs updating though.

5. Low dust operation. I have found next to none in my boiler room. The fly ash does fall to the floor under the unit, a flaw described in the Bureau of Mines report. Less than a cup of granular fly ash. I can live with it.

6. Good fines control: they settle under the pick up tube and become the "hopper bottom" of your bin. Probably have to deal with them every few years or so. About a cupful of fines collect in the feed tube head but are contained there indefinitely. The peas and excess fines continue on to the fire pot.

7. Pete Axeman is not a salesman. He's an engineer and manufacturer. I appreciate the soft sell. He was outstanding to work with and quite available directly for questions.

8. Lifetime warranty (vessel and grate).

9. Some early units are still in operation.

10. Steel Boiler vessel. In fact, everything is heavy steel. Very heavy steel.

11. ASME code design. (required in my area) AHS is non-code for the same $$$. AHS will provide a stamp for extra $$$.

12. Extremely rugged. If it breaks though, it likely can be fixed without major troubles.

13. Controls are standard boiler except anthrastat.

14. Pea sized coal is in less demand than rice. Pea burns with less gas build up, i.e. combustion bumps are nil. (not so with buckwheat which can be burned in the AA with a slight modification)

15. Set and forget operation. (excluding, of course, the thusfar twice a week jump in the coal bin to shovel coal for 90 seconds and the once a week trip with the ash bins to the landfill.) I started the fire Nov 7, 2007. In about 35-45 minutes my fire pot was full and the boiler was heating my house and hot water. I haven't had to do much since. (What a let down from my 18 months of immersion in this topic designing my boiler/radiator system from scratch -- LOL--I was almost diappointed there were no problems to manage!)